/Engine/Source/Runtime/RenderCore/Public/RenderGraphBuilder.h
A variant where InitialData and InitialDataSize are supplied through callbacks. This allows queuing an upload with information unknown at creation time. The callbacks are called before RDG pass execution so data must be ready before that.
void QueueBufferUpload ( FRDGBufferRef Buffer, FRDGBufferInitialDataCallback && InitialDataCallback, FRDGBufferInitialDataSizeCallback && InitialDataSizeCallback )